Ultrasound has received widespread acceptance as a useful diagnostic tool by providing an image of the internal area of inquiry by emission of very high frequency sound waves from a transducer (commonly called a “probe”) placed in contact with the patient's skin adjacent that area of inquiry. Repeated arrays of ultrasonic beams scan that area and are reflected back to the transducer, where the beams are received and the data transmitted to a processing device. A processing unit, to which the probe is connected, analyzes the information and composes a picture for display on an associated monitor screen. For some applications the determination of the precise position or location of the probe with respect to the patient's body is desirable, e.g., to correlate the ultrasonic image to other scans, such as CT scans.
So-called “3D tracking” systems are commercially available and disclosed in the patent literature for enabling one to readily determine the 3D position of an instrument, such as a medical device, by determining location, orientation, and/or positioning information relative to some coordinate system. For example, Ascension Technology Corporation makes 3D position and orientation tracking devices suitable for various medical applications, e.g., to navigating, localize, and guide medical instruments for image-guided procedures. Other manufacturers/suppliers of 3D tracking systems include Polhemus, Inc. Northern Digital Inc. and Medtronic, Inc.
Typically 3D tracking systems use the attenuation of oriented electromagnetic signals to determine the absolute position and orientation of a sensor, relative to a source, e.g., a DC magnetic field generator. The source and the sensor are connected via cables to an electronics module, which contains a microcomputer and associated electronics of the system. The source typically includes three orthogonal coils that are pulsed in rotation, one after another. Each pulse transmits a radio frequency electromagnetic signal that is detected by the sensor. The sensor also contains three orthogonal coils, which measure the strength of the signal from the current source coil. By using the known pulse strength at the source and the known attenuation of the strength with distance, the position and orientation of the sensor coils can be calculated by the system via triangulation techniques.
Utilizing device location or 3D tracking systems with ultrasonic probes can be accomplished by permanently mounting the sensor(s) on the probe or by building such sensor(s) into the probe. However, this approach may not be desirable if the probe is also intended to be used in applications wherein its position need not be determined, since the inclusion of such sensor(s) permanently on or in the probe will likely increase the cost and complexity of the probe. Moreover, such an approach may not be suitable to retrofit existing ultrasonic probes. Thus, the use of some releasable mounting system is deemed to be the better approach for providing an ultrasonic probe with means for determining its position with respect to the patient's body.
As will be appreciated by those skilled in the art, the prior art includes various brackets for releasable mounting devices on an ultrasonic probe. Such brackets are commonly used to support biopsy needle guides and the like. Examples of such brackets are disclosed in U.S. Pat. No. 5,052,396 (Wedel et al.), U.S. Pat. No. 5,076,269 (Arenson et al.), U.S. Pat. No. 5,623,931 (Wung et al.), U.S. Pat. No. 5,758,650 (Miller et al.), U.S. Pat. No. 5,941,889 (Cermak), U.S. Pat. No. 6,379,307 (Filly et al.), and U.S. Pat. No. 7,087,024 (Pruter). My prior U.S. Pat. No. 5,941,889 (Cermak) discloses and claims a multiple angle disposable needle guide system for use in guiding needles into selected locations of a patient relative to an ultrasonic probe or some other medical instrument imaging sensor.
While such brackets are suitable for their intended purposes, they are not designed for mounting one or more position sensors thereon. Accordingly, a need exists for such a bracket. Moreover, that bracket should be constructed so that the sensor(s) when mounted thereon will be resistant to accidental displacement, but can be readily removed and/or mounted when desired. This invention addresses those needs.
All references cited herein are incorporated herein by reference in their entireties.